Capacitor discharge battery charger

ABSTRACT

A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging the capacitor, and means for alternately charging the capacitor from said power source and discharging it to the battery and therefore to charge said battery.

United States Patent Inventor John c. Lesher 7 Erie, Pa. Appl. No. 867,679 Filed Oct. 20, 1969 Patented July 20, 1971 Assignee Teledyne, Inc.

Los Angeles, Calif.

CAPACITOR DISCHARGE BATTERY CHARGER l 1 Claims, 2 Drawing Figs. US. Cl 320/21, 320/39, 321/2, 320/] int. Cl "02] 7/02 Field of Search 320/ 19, 2224, 39,40, BIG. 1, DIG. 2, 1, l7; 32ll 2; 331/1 17 [56] References Cited UNITED STATES PATENTS 3,252,070 5/l966 Medlar et al ..320/DlG. 2 UX 3,305,755 2/1960 Walsh ..320/DIG. 2 UX 3,376,488 4/1968 Walsh ..320/D]G. 2 UX .Primary Examiner-J. D. Miller Assistant Examiner-John M. Gunther Attorney-Olson, Trexler, Wolters & Bushnell ABSTRACT: A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging the capacitor, and means for alternately charging the capacitor from said power source and discharging it to the battery and therefore to charge said battery.

CAPACITOR DISCHARGE BATTERY CHARGER SUMMARY THE INVENTION This invention relates generally to a battery charger and more particularly to an automobile capacitor discharge battery charger.

DISTINCTIONS OVER PRIOR ART ANDOBJECTS practical since the vehicle maynot be near a convenient outlet. I

it would be ideal if this same trickle charge could prevail even while the vehicle iszparked. However, if the battery was run down caused by short trips ahigher charging current will be needed to regain the gravity level.

Most prior art battery charges charge continuously although often at a variable rate. A somewhat different approach is disclosed in accordance with U.S. Pat. No. 3,252,070 to Medler et al. The Medler et al. batterycharger is of the pulse charge type. The chief object of thistype of battery charger is to charge a battery intennittentlyaleaving an idle time between charges, hence the term pulse. charge."

With particular regard to the Medler charger, two primary circuits make upthe invention. A charging circuit of a conventional type is utiliied to supply-power directly from a power source to the battery. Secondly, a timing and switching circuit connects the charging circuit. to-the battery periodically. The charging'source. is taken fromva stepdown transformer connected to a switch means suchasa motor-driven timer, a gas discharge tube, atransistor. ora silicon controlled rectifier. The timing is established by an RC circuit connected to the battery pack is included in the charger housing making it a self-contained unit. 1 1

Yet another object of the present invention is to provide an improved battery charger which uses a capacitor discharge circuit to charge a battery. I

These and other objects and features of the invention will become more apparent from a reading of the following descriptions.

BRIEF DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION 7 Attention should first be directed to FIG. 1 in connection with the following brief description as to how the present gate of the controldevice. The-concept of the Medler inven- I tion relates to charging of the battery and maintaining the charge periodically while the battery is idle or in storage.

A common problem in the pulse-charge-type battery charger, forexample Medler etal-., is. the high current which must necessarily be derived from;a.source tocharge the battery being charged. This high current requirement is necessary because the Medler-type battery charger charges a battery directly from its source of power, periodicallycutting this power off by means of its timing and switching circuit. Therefore, the amount of current utilized by the battery being charged must be equal to the amount of current derived from the source, and this could be extremely large.

A second common problem in. the pulse-type battery charger of the prior art is related to the problem discussed above. Specifically, since this type of battery charger charges its battery with current directly. from the power source and since such current may be extremely high in value, an outside power source is necessary. This becomes extremely inconvenient and costly when the battery being charged is that of an automobile battery. The prior' art. battery charger generally uses an independent source which in the case of automobile battery charging is generally. located in a garage of the automobile-owner. The power may however be derived directly f from the owner's house. In either case, the charging stage can only take place while the automobile is parked in the garage or adjacent to the house.

Therefore, a general object of the present invention is to provide an improved battery charger which overcomes the limitations of the prior art by utilizing a low input current for charging a battery. 7

Another general object of thepresent invention is to charge I a battery using a small battery pack as a power source, which capacitor discharge battery charger 10 operates. The circuit as a whole comprises three functional subcircuits which interact with each other ultimately to charge a battery. The first subcircuit 12 consists of a resonant feedback oscillator circuit, a step-up transformer circuit, and a capacitor discharge circuit. The second subcircuit 14 which is connected across the output of the first subcircuit consists of a unijunction transistor circuit. Attached to the output of the unijunction transistor circuit is athird subcircuit 16 which includes two transistors tied appropriately to each other to function as a saturated switch. The output of the entire circuit is connected to the battery being charged. 1

The resonant feedback oscillator circuit which is of a known kind is powered by a battery source which may be a small battery pack'included in the battery chargers housing making the battery charger a self-contained unit 10. The output of the resonant feedback oscillator is applied to the step-up transformer circuit whose output is used'to-charge a capacitor contained within the capacitor discharge circuit which capacitor quickly discharges its current to the battery being charged. The oscillator circuit supplies a low current output to the stepup transformer which developesapproximately 40 volts AC across its secondary winding. The'capacitor has a constant of approximately 18,000microfarads and requires approximately 10 seconds to becharged to its full capacity. The capacitor maythereafter discharge approximately 2% amps to a l2-volt battery being charged in about one-fourth of a second. These values may, of course, be changed-if a battery other than a i2- volt-battery is being charged.

The second subcircuit which is made up of a unijunction transistor circuit is used to determine when the capacitor of the first subcircuit has obtained its capacity. When this has occurred the unijunction transistor circuit delivers a pulse to the input of the third subcircuit 16 which acts as a saturated switch creating a direct path from the capacitor to the battery for allowing the capacitor to discharge directly into the battery being charged.

ln summarizing the above, a battery which has lost its charge due to use is appropriately connected to the capacitor discharge charger 10 which is housed as a self-contained unit. Thecharger may, for example be connected to the cigarette lighter'receptacle. A power source contained in the housing, preferably a small battery pack, emits a low current output over a period of time (approximately 10 seconds) which chargesa capacitor to its full capacity via a resonant feedback oscillator and step-up transformer. When the capacitor has charged to full capacity the unijunction timing circuit of the second subcircuit actuates the saturating switch arrangement of the third subcircuit to allow the capacitor to discharge its stored'energy to the battery. Since the discharging process of torsCl'and C2. I v a Since the resonant feedback oscillator arrangement is of a conventional type it is not necessary to discuss particular the capacitor takes much less time (one-fourth of a second) than 'the charging of said capacitor (approximately 10 seconds) the current ultimately delivered to the battery (2% subcircuit l4 and'a third subcircuit 16 which is connected to a l2-volt battery being charged. V

The first subcircuit 12 includes a resonant feedback oscillator circuit 18 powered by a battery source 20 and connected to the primary winding 22 ofa step-up transformer 24. The

capacitor discharge circuit 26 is connected across the secondary winding 28 of transformer 24;

tor 560i transistor 49. The emitter 54 of transistor 49 is connected tothe'di'scharge side of capacitor C3. The resistor 51 is 7 connected at one end to the collector 56 of transistor 49 and I at its other end to the positive side of the battery being The resonant feedback oscillatorcircuit is of a conventional vtype which includesa transistor 29 with its collector 30 connected to the positive side of battery 20, its emitter 32 convnected to the primary winding 22 of transformer 24 by a movable tab 33 and its base 34 connected intermediate the negative side ofbattery and one side of primary'winding 22 through a resistor 31. Two capacitors C1 and C2 are placed in "series and have one end thereof connectedintermediate the base34 oftransistor 29 and resistor 31 and the other end connected intermediate the negative side of battery 20 and one side of primary winding 22. One side of primary winding 22 is 7 connected to the negative side of battery 20 and the other side of theprimary winding is connected intermediate the capacivalues of the individual elements therein. Functionally, the movable tab 33 is so positioned on the primary, winding 22 .that the step-up-transformer 24 has an output of approximately 40 volts AC across its secondary windings 28.

' The capacitor discharge arrangement 26 comprises -a capacitor C3 connected acros the secondary windings 28 of transformer 24 through a diode D1 which rectifies the AC output of the stepup transformer and the resistor 35 which limits the current that charges the capacitor C3. As stated above, the

capacitor C3 has a value of 18,000 microfarads and has the ability to store *upto 2% amps which may ultimately .be

discharged to a 1'2-volt battery being charged.

The second subcircuit '14 is connectedacross the capacitor C3 and comprises a unijunction transistortiming circuit 34. The unijunction transistor timing circuit comprises a unijunction transistor 36 with emitter 38, base 40 and base 42, a capacitor C4 and resistors 41, 43- and 45. The emitter 38 of unijunction transistor36 is connected intermediate the resistor.4l and capacitor C4 which are connected in series across the capacitor C3. The base 40 of unijunction 36 is connected to one end of resistor 43 which is connected parallel to resistor 41 and base 42 is connected to one end of resistor 45 which is connected parallel to capacitor C4.

' Functionally, the capacitor C4 is charged by a limited current'fro m' the output of step-up transformer 24. The current used to charge C4 is limited by resistor 41 thus allowing the majority of this current to charge capacitor C3. When capacitor C3 has obtained its full charge, i.e. when it has enough energy stored to discharge at approximately 2% amps, the capacitor C4 will discharge through the emitter 38 of unijunc,-

v The third subcircuit 16 which consists of a saturating switch circuit 34is connected across the output of unijunction transistor 36. The saturating switch'circuit consists of an NPN- type transistor 47 with base 46, emitter 48 and collector 50, a FNP-type transistor 49 with base 52, emitter 54 and collector '56 and a limiting-resistor 5].

' being chargedsThe limiting resistor 51 protects the transistor 49 from high surge current. As long as the capacitor C4 continues to discharge current to the base 46 of 47, 49 will maintain its conductive state allowing C3 to discharge to the bat tery being charged. I

In order that the unique aspects of applicant's invention may be more fully appreciated, a discussion of its operation as a whole will now be given. I

, The capacitor discharge battery charger is connected across the battery being charged. if, for example, the battery being charged is an automobile battery, the charger may be plugged into the cigarette lighter receptacle of the automobile as a quick convenient connection, or it may be installed permanently in the vehicle. 7 a 1 The battery 20 of the capacitordischarge battery charge 10 supplies power to the resonant feedback oscillator 18 which in turn is used by the step-up transformer 24 to provide an output voltage of 40 volts AC across its secondary windings 28. This in turn provides a small current through the rectifying diode D1 and limiting resistor 35 for charging capacitor C3 and capacitor C4. However, due to resistor'4l only a small portion of this current'will be directed to capacitor C4. Since the transistor 49 at this point is in a nonconduction state, no current will pass to the battery. The timing capacitor C4 is of appropriate value to allow capacitor C3 to charge to, its full capacity before discharging to the battery. When the capacitor C3 has charged to its full capacity the capacitor C4 discharges through the unijunction transistor 36 andto the base 46 of transistor 47. This allows the transistor 49 to go from a nonconduction state to-a full conduction state so that the capacitor C3 may discharge through the transistor 49 and resistor 51 to the battery being charged. Since the time required for the capacitor C3 to discharge ismuch less than that time required for it to be charged, the current which is delivered to the battery isof a much greater amplitude than that current used to charge the capacitor C3. v

While particular embodiments of the invention have been shown, it should be understood, of course, that the invention is not limited thereto since many modifications may be made and it is therefore contemplated to cover by the present application and such modifications that fall within the true spirit and scope of the appended claims.

The invention 1 claim is as follows:

1. A capacitor'discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging said capacitor, means for alternately charging said capacitor from said power source and discharg- The'transistor 47 has its base 46 connected the base 42 of unijunction transistor 36 while its collector 50 is connected to the base 52 of 49 and its emitter48 is connected to the collec- '5.

ing it to said-battery and therefore to charge said battery, a resonant feedback oscillator circuit and a transformer electrically connected intermediate said source of power and said capacitor whereby a low current may be maintained to charge said capacitor, said charging and discharging means including a unijunctiontransis'tor timing circuit for determining when said capacitor has reached a predetermined charge, and a saturated switching circuit for discharging said capacitor'to said battery when said capacitor has'reached its predetermined charge, said unijunction'transistor timing circuit and switching circuit being electrically connected intermediate battery is of greater magnitude than the charge to said capacitor.

2. A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging said capacitor, means for alternately charging said capacitor from said power source and discharging it to said battery and therefore to charge said battery, said charging and discharging means including a unijunction transistor timing circuit for determining when said capacitor has reached a predetennined charge, and a saturated switching circuit for discharging said capacitor to said battery when said capacitor has reached its predetermined charge, said unijunction transistor timing circuit and switching circuit being electricallyconnected intermediate said capacitor and said battery whereby the discharge to said battery is of greater magnitude than the charge of said capacitor.

3. A capacitor discharge charger according to claim 1 wherein said unijunction transistor circuit includes a second capacitor connected across the first capacitor and a unijunction transistor means connected intermediate said second capacitor andsaid switching circuit whereby said second capacitor charges in the same manner as said first capacitor and discharges a current signal through said unijunction transistor means to said switching circuit for allowing said first capacitor to discharge to said battery.

4.,A capacitor discharge charger according to claim 3 wherein said switching circuit includes a first transistor electrically connected to said unijunction transistor means for receiving said discharge signal and a second transistor electrically connected to said first transistor whereby said second transistor becomes fully conductive allowing said first capaci- A tor to discharge to the battery when said first transistor receives said signal.

5. A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery being charged, a source of power for charging said capacitor and means for alternately chargingsaid capacitor from said power source and discharging it to said battery and therefore to charge said battery, said last-'mentionedmeans including a ing circuit for determining when said capacitor has reached a predetermined charge and a saturated switching circuit for discharging said capacitor to said battery when said capacitor has v reached its predetermined charge, said unijunction transistor timing circuit and switching circuit being electrically connected intermediate .said capacitor and said battery whereby the discharge to said battery is of greater magnitude than the charge to said capacitor, said unijunction transistor circuit including a second capacitor connected across the first-mentioned capacitor and a unijunction transistor means unijunction transistor timconnected intermediate said second capacitor and said switching circuit whereby said second capacitor charges in the same manner as said first capacitor and discharges a current signal through said unijunction transistor means and said switching circuit for allowing said first capacitor to discharge to said first battery and said switching circuit includes a first transistor electrically connected to said unijunction transistor means forreceiving said discharge signal and a second transistor electrically connected to said first transistor whereby said second transistor becomes fully conductive allowing said first capacitor to discharge to the battery when said first transistor receives said signal.

6. The method of charging a battery comprising the steps of supplying a low current to a capacitor for a period of time to charge said capacitor substantially to a predetermined potential, discharging a higher current from said capacitor to the battery to be charged at a predetermined point in time when the capacitor has substantially reached its predetermined chargcand over a shorter period of time than required to charge said capacitor, said method further including the step of charging a second capacitor in the same manner as the first capacitor and discharging a current signal from said second capacitor to a switching circuit and thereby to discharge said capacitor through said switching circuit to said battery at said predetermined point of time.

7. A capacitor discharge battery charger comprising a capacitor, means for charging a capacitor from a source of power at a predetermined relatively low rate, an output circuit connected to said capacitor and adapted to be connected to a battery to be charged and including a controlled electronic switch is circuit with said capacitor and having a control element for holding said switch off or for turning it on to discharge said capacitor at'a relatively high rate to a battery to be charged, and a timing circuit connected in circuit with said capacitor and to said control element for turning said electronic switch on when said capacitor substantially reaches a predetermined potential.

8. A battery charger as set forth in claim 7 wherein the timing circuit comprises'a resistance-capacitance timing circuit.

9. A battery chai'ger as set forth in claim 8 wherein said output circuit further includes an electronic switch device connected to said resistance-capacitance timing circuit and to the control element of said controlled electronic switch.

10. A battery charger as set forth in claim 7 wherein the means for charging the capacitor comprises a two-element rectifying device.

11. A battery charger as set forth in claim 7 and further ineluding a source of power comprising a battery, an oscillator connected to and powered by said battery, and a rectifier in- 

1. A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging said capacitor, means for alternately charging said capacitor from said power source and discharging it to said battery and therefore to charge said battery, a resonant feedback oscillator circuit and a transformer electrically connected intermediate said source of power and said capacitor whereby a low current may be maintained to charge said capacitor, said charging and discharging means including a unijunction transistor timing circuit for determining when said capacitor has reached a predetermined charge, and a saturated switching circuit for discharging said capacitor to said battery when said capacitor has reached its predetermined charge, said unijunction transistor timing circuit and switching circuit being electrically connected intermediate said capacitor and said battery whereby the discharge to said battery is of greater magnitude than the charge to said capacitor.
 2. A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery to be charged, a source of power for charging said capacitor, means for alternately charging said capacitor from said power source and discharging it to said battery and therefore to charge said battery, said charging and discharging means including a unijunction transistor timing circuit for determining when said capacitor has reached a predetermined charge, and a saturated switching circuit for discharging said capacitor to said battery when said capacitor has reached its predetermined charge, said unijunction transistor timing circuit and switching circuit being electrically connected intermediate said capacitor and said battery whereby the discharge to said battery is of greater magnitude than the charge of said capacitor.
 3. A capacitor discharge charger according to claim 1 wherein said unijunction transistor circuit includes a second capacitor connected across the first capacitor and a unijunction transistor means connected intermediate said second capacitor and said switching circuit whereby said second capacitor charges in the same manner as said first capacitor and discharges a current signal through said unijunction transistor means to said switching circuit for allowing said first capacitor to discharge to said battery.
 4. A capacitor discharge charger according to claim 3 wherein said switching circuit includes a first transistor electrically connected to said unijunction transistor means for receiving said discharge signal and a second transistor electrically connected to said first transistor whereby said second transistor becomes fully conductive allowing said first capacitor to discharge to the battery when said first transistor receives said signal.
 5. A capacitor discharge charger for charging a battery comprising: a capacitor electrically connected intermediate a source of power and the battery being charged, a source of power for charging said capacitor and means for alternately charging said capacitor from said power source and discharging it to said battery and therefore to charge said battery, said last-mentioned means including a unijunction transistor timing circuit for determining when said capacitor has reached a predetermined charge and a saturated switching circuit for discharging said capacitor to said battery when said capacitor has reached its predetermined Charge, said unijunction transistor timing circuit and switching circuit being electrically connected intermediate said capacitor and said battery whereby the discharge to said battery is of greater magnitude than the charge to said capacitor, said unijunction transistor circuit including a second capacitor connected across the first-mentioned capacitor and a unijunction transistor means connected intermediate said second capacitor and said switching circuit whereby said second capacitor charges in the same manner as said first capacitor and discharges a current signal through said unijunction transistor means and said switching circuit for allowing said first capacitor to discharge to said first battery and said switching circuit includes a first transistor electrically connected to said unijunction transistor means for receiving said discharge signal and a second transistor electrically connected to said first transistor whereby said second transistor becomes fully conductive allowing said first capacitor to discharge to the battery when said first transistor receives said signal.
 6. The method of charging a battery comprising the steps of supplying a low current to a capacitor for a period of time to charge said capacitor substantially to a predetermined potential, discharging a higher current from said capacitor to the battery to be charged at a predetermined point in time when the capacitor has substantially reached its predetermined charge and over a shorter period of time than required to charge said capacitor, said method further including the step of charging a second capacitor in the same manner as the first capacitor and discharging a current signal from said second capacitor to a switching circuit and thereby to discharge said capacitor through said switching circuit to said battery at said predetermined point of time.
 7. A capacitor discharge battery charger comprising a capacitor, means for charging a capacitor from a source of power at a predetermined relatively low rate, an output circuit connected to said capacitor and adapted to be connected to a battery to be charged and including a controlled electronic switch is circuit with said capacitor and having a control element for holding said switch off or for turning it on to discharge said capacitor at a relatively high rate to a battery to be charged, and a timing circuit connected in circuit with said capacitor and to said control element for turning said electronic switch on when said capacitor substantially reaches a predetermined potential.
 8. A battery charger as set forth in claim 7 wherein the timing circuit comprises a resistance-capacitance timing circuit.
 9. A battery charger as set forth in claim 8 wherein said output circuit further includes an electronic switch device connected to said resistance-capacitance timing circuit and to the control element of said controlled electronic switch.
 10. A battery charger as set forth in claim 7 wherein the means for charging the capacitor comprises a two-element rectifying device.
 11. A battery charger as set forth in claim 7 and further including a source of power comprising a battery, an oscillator connected to and powered by said battery, and a rectifier interconnecting said oscillator circuit and said capacitor. 